The Japanese archipelago is situated on volcanic chains, and the occurrence of a massive earthquake disaster is therefore a major concern in the oceans to the east, southeast and south, not to mention throughout the archipelago. To protect the lives and property of citizens from earthquake disasters, more suitable measures must be taken not only for systems for recovery following an earthquake, but for earthquake prediction, and for this purpose, the establishment of a low-cost, and moreover, highly accurate and effective earthquake prediction technology is urgently required.
From ancient times, many examples of precursors of impending earthquakes have been reported, such as the agitated behavior of catfish or the increased activity of rats. In addition, several days before the Great Hanshin-Awaji (Kobe) Earthquake and Fire of January 1995, local amateur radio operators observed radio-wave abnormalities, and a phenomenon known as an “earthquake cloud” was witnessed by many people.
It is believed that the occurrence of such radio-wave abnormalities and “earthquake clouds” result from some form of influence of telluric currents that are in turn generated by the piezoelectric effect resulting from the collision of tectonic plates.
The prediction of earthquakes by observing the amount of rotation of a permanent magnet that is suspended from a thread has been disclosed (for example, in Japanese Patent Laid-Open Publication No. H11-258353).
However, the prediction of earthquakes with high accuracy by observing changes in telluric current would necessitate the establishment of a large number of closely-spaced observation facilities over an extensive observation area. As an example, earthquake prediction in the eastern seaboard region of Japan would require an observation system covering several hundred kilometers square.
With the current financial difficulties faced by national and municipal governments, such an establishment of a large number of observation facilities would be a tremendous burden, and the costs for maintaining and operating the observation system would render the realization of such a system highly problematic.